The present invention relates to structural support systems, such as those used in buildings and bridges. More specifically, the invention relates to a structural support system designed to achieve composite action and meet OSHA safety regulations.
As of Jul. 15, 2001, safety regulations imposed by OSHA on the steel structure and bridge industry have forced the industry to make a dramatic change. The required change deals with the way in which structural support systems are constructed. Structural members, such as composite steel beams and plate girders, are the main load-carrying members in structural support systems. The structural members are usually placed on supports, and a concrete slab is then cast on top of them. In nearly all cases, mechanical connectors are provided so that the structural members act in conjunction with the concrete in resisting applied loads. Such a result is commonly referred to as the steel-concrete composite action of the system.
The current practice of developing the composite action between the structural members and the concrete is to weld a shear stud or transversely placed plate or channel to the top of the structural member. There have also been suggestions of developing the composite action by placing a discontinuous plate along the beam length with large holes in the plate. All of these alternatives may be hazardous, as explained below, and do not pass OSHA safety requirements.
The typical construction sequence of the prior art involved welding shear studs to structural members in the shop, transporting the structural members to the field, and placing them on supports. The shear studs were welded to the top flange of each beam such that the studs extended upward from the flange. After the structural members were placed on the supports, workers walked on the top surface of the structural members (between the shear studs), placing formwork (a temporary support for wet concrete) between adjacent structural members. The concrete was then poured over the structural members and formwork.
A safety concern exists for workers required to walk on the top surface of the structural members. Workers may easily trip on the shop-welded shear studs, because of the limited space available for walking, and be severely injured or killed. This is the primary rationale for OSHA's mandate that shear studs be welded while in the field. Although this mandate may solve the problem of workers tripping on shop-welded shear studs, the industry is hesitant to weld in the field. Field welding is expensive and, in general, is of a lower quality than welding produced in the shop. The preference, therefore, is to do all welding in the shop before the structural members are shipped to the field.
In order to overcome these disadvantages, a method and apparatus for reinforcing concrete structures is needed that will meet OSHA safety requirements and allow for welding to be done in the shop.